Detection techniques and related methodologies have been and remain active areas of research in a wide range of diverse fields. While selectivity is a primary concern, sensitivity can be equally as important, depending upon the particular end-use application. As common as those issues may be, such detection methods inevitably vary with regard to sensor theory, design and/or operation. An approach to one particular analyte is often unsatisfactory, if effectual at all, with respect to another.
For instance, consider mercury poisoning, a significant threat to human health. In the United States, nearly 87% of mercury emissions result from solid waste incineration and the combustion of fossil fuels. The long atmospheric lifetime of mercury causes contamination across vast quantities of land and water. To make the problem worse, bacteria convert elemental and ionic mercury to methyl mercury adding this potent neurotoxin to the food chain. Mercury poisoning causes serious sensory, motor and cognitive disorders in human beings.
Knowing the seriousness of this problem, significant research efforts have been devoted to improving mercury detection. Current industrial approaches rely on costly, time-consuming methods like atomic absorption/emission spectroscopy or inductively coupled plasma mass spectroscopy, which are not very amenable to portable, convenient “in the field” detection. Therefore, many laboratories have focused on “colorimetric,” redox-active, and/or fluorescence chemosensors in the hopes of developing new mercury sensors. Many such sensors are affected by competing metal ions, are incompatible with aqueous media and/or have slow HgII response times. In all cases, it is critical to selectively detect mercury in the presence of other environmental metals especially PbII and CuII.
By comparison, a variety of approaches to detect nerve agents have been reported including those based on colorimetric, fluorimetric, gas chromatography and enzymatic assays. A common limitation of these approaches is their general lack of selectivity and/or sensitivity. To make the problem more complex, G-type and V-type agents are organophosphates (OPs); the same chemical class as many widely used pesticides so that detection of the nerve agents typically must complete with a background level of OPs. From a practical sense, colorimetric detection is generally considered simplest since it just requires a color change to be monitored. However, as sensitivity is an issue, fluorescence based sensors can have the potential for wide-range use and application.
As evident from the preceding, a method for mercury detection may not be applicable in or entirely suitable for sensing nerve agents. As a result, the search for a broad-based effective, selective and sensitive molecular approach to a range of detection systems remains an on-going concern in the art.